Hmm, would it stack or be a second check if the spell caster is also being damaged by other spells?
Nasty senerio, Force Cage (bars), Dimension Lock, Acid Fog, Incendiary Cloud, Cloud Kill.
Would there be just one concentracion check or would the damaging spells force a check and the Cloud Kill force a different check?
Yea, I thought it would be wierd for a higher level caster to be forced to make a higher DC concentration check, but then again, they have higher concentration too.